1. Field of the Invention
This invention relates to a multi-type air-conditioning apparatus having a plurality of air-conditioning units connected to an outdoor unit. 2. Description of the Related Art
A multi-type air conditioning apparatus having a plurality of indoor units connected to an outdoor unit is known. For example, such a multi-type air-conditioning apparatus is disclosed in Japanese Patent Disclosure No. 1-203856 and U.S. Pat. No. 4,926,652.
Further, an air conditioning apparatus having a plurality of personal air-conditioning units instead of a plurality of indoor units is provided. The personal air-conditioning units are disposed on a large number of desks are installed in a room, for example, to separately air-condition various spaces in the room.
When the air conditioning apparatus having a plurality of personal air-conditioning units is installed in an office of a building, the refrigerant pipe and drain pipe are generally disposed in the space under the floor. Such a space is called a free access floor.
However, a free access floor is originally provided for accommodating electrical, wirings for a computer and business machines. The depth of the floor thereof is set to at most approx. 10 cm. The depth imitation is imposed on the free access floor because if the difference between the room floor and the corridor floor becomes too large, it creates an inconvenience when going into or out of the room. Also, ceiling of the room becomes relatively low creating a sense of oppression when the depth of the free access floor is set excessively large.
When the drain pipe is disposed in such a free access floor, the inclination of the drain pipe cannot be made large. Therefore, dust will tend to be deposited in the drain pipe and the pipe will be clogged with the dust.
In order to solve the above problem, a method of forming an opening in the concrete slab lying below the free access floor and extending the drain pipe to the lower floor via the opening is considered.
However, with the above method, it is necessary to form a new opening in the concrete slab each time the arrangement of the desks disposed on the floor is changed and to fill up the old opening. This construction work is extremely troublesome.
As is disclosed in Japanese Patent Disclosure No. 2-302532, a cooling system having cooling units provided for a plurality of heat-generating units installed on the same floor is proposed. In this case, it is also difficult to provide adequate drainage in the limited space.
The capacity of the personal air-conditioning unit is approx. 0.1 to 0.5 horse power. In contrast, the capacity of a compressor in an outdoor unit is 5 to 10 horse power. The capability controlling range of the compressor of this class is approximately one horse power at minimum, even in an inverter-driven type compressor.
Therefore, when only one personal air-conditioning unit is used, it is necessary to save the capability thereof to approximately 0.1 horse power in order to set up a comfortable air-conditioned environment with less temperature variation. This is impossible to do.